Earthwork Volume Calculation, 3D Model Generation, and Comparative Evaluation Using Vertical and High-Oblique Images Acquired by Unmanned Aerial Vehicles

Abstract

In civil engineering and building construction, the earthwork volume calculation is one of the most important factors in the design and construction stages; therefore, an accurate calculation is necessary. Moreover, because managing earthworks is highly important, in this study, a three-dimensional (3D) model for earthwork calculation and management was performed using an unmanned aerial vehicle (UAV) and an RGB camera. Vertical and high-oblique images (45°, 60°, and 75°) were acquired at 50 and 100 m heights for accurate earthwork calculations and a 3D model, and data were generated by dividing the images into eight cases. Cases 1–4 were images acquired from a height of 50 m, and cases 5–8 were images acquired from a height of 100 m. (case 1: 90°, case 2: 90° + 45°, case 3: 90° + 60°, case 4: 90° + 75°, case 5: 90°, case 6: 90° + 45°, case 7: 90° + 60°, case 8: 90° + 75°). Three evaluations were performed on the data. First, the accuracy was evaluated through checkpoints for the orthophoto; second, the earthwork volumes calculated via a global positioning system and UAV were compared; finally, the 3D model was evaluated. Case 2, which showed the lowest root mean square error in the orthophoto accuracy evaluation, was the most accurate. Case 2 was the most accurate in the earthwork volume evaluation and 3D model compared to other cases. Through this study, the best results were obtained when using a vertical image and a high-oblique image of 40 to 50° when generating a 3D model for earthwork volume calculation and management. In addition, if the UAV is not affected by obstacles, it is better to shoot at about 50 m or less than to shoot the UAV height too high.

Stockpile Volume Estimation in Open and Confined Environments: A Review

“…Idrees and Abdulrahman [60] conducted the aerial survey at different flight altitudes, and the error in the estimated volume between the two methods was minor (<0.3%). On the other hand, Lee and Lee [52] showed that the estimated volumes from GNSS-RTK and drone photogrammetry had a difference of 2%. However, clearly, the hours of surveying needed while using the GNSS-RTK technology can be avoided when using drones that can reduce the mission time to just few minutes.…”

“…Drone photogrammetry is generally seen as a faster and safer solution for monitoring and volume estimation. For instance, drone photogrammetry was applied in missions for dump and landfill waste management [38], earthwork in mining and quarrying [52,53], and agriculture [10]. Table 1 summarizes drone photogrammetry-based approaches for stockpile/earthwork volume estimation that appeared in the literature since 2020.…”

“…Other studies, such as those conducted by Idrees and Abdulrahman [60] and Lee and Lee [52], considered estimating the volume of a dam using drone photogrammetry while comparing the results to that produced from the GNSS-RTK method. To ensure accurate volume estimation by the GNSS-RTK, multiple measurements at different locations on the dam were obtained to account for any variations in the shape.…”

“…As expected, Rohizan et al [61] showed that a lower altitude setting produces high volumetric error. Conversely, Idrees and Abdulrahman [60] reported that flying at 25 m produced better results than flying at 50 or 100 m. Lee and Lee [52] similarly found that flying at 50 m provided better estimation than flying at 100 m. However, these results are subjective and are potentially misleading, having produced their results in absolute figures. As a result, some researchers have determined altitude requirements in relative rather than absolute terms.…”

Calculation Model of Earthwork Volume in Open Pit Mined Area Based on Step Feature Line

“…For example, the calculation method of earthwork volume based on irregular triangular network model, proposed by Papa I through tilt photogrammetry technology of UAV [3]. An optimization algorithm for constructing fine irregular triangular networks, proposed by Wang C based on spatial constraint information [4]; Delaunay triangular network construction method based on contour constraints, proposed by Lee K [5]. However, when the terrain model of open pit mined area is constructed by unconstrained irregular triangulation method, the complex terrain features may not be expressed correctly.…”